The Mugen 2 is compatible with the "
Gigabyte GA-790FXTA-UD5" motherboard and "
Antec Sonata Designer 500" case (this is a fairly small case). Since I use the low power "AMD Phenom II X4 905e Deneb 2.5GHz AM3 65W Quad-Core Processor" I don't even use a fan. This heatsink alone is enough to keep my CPU cool even after 24 hours of prime95 (46C). However, if you did use the included fan it would cover the first two blue RAM banks. I.e. the RAM would work fine, the fan would just be hanging over the RAM. Therefore if you ever had to swap your RAM out you'd need to take the fan off first. If you had extra tall RAM you might have to bump the fan up just a bit, but it should still work fine.
Just FYI the RAM I use is
CT2KIT25672BA1339 - 4GB kit (2GBx2), 240-pin DIMM , DDR3 PC3-10600 from Crucial.com.
This is ECC RAM.
I've attached 3 pics of my installed Mugen 2.